Application Of Ti₃C₂T_x And Its Composite Materials In The Field Of Supercapacitor

With the popularity of various portable electronic products,energy storage equipment can not meet the needs of people gradually,so the research of energy storage devices has become a trend in the field of science and technology.As an indispensable part of energy storage devices,supercapacitors have attracted extensive attention from researchers due to their high power density and cycle stability.As an important component of supercapacitor,electrode material plays a key role in the performance of supercapacitor.Therefore,it is necessary to develop electrode material vigorously.Two-dimensional transition metal carbon/nitride（MXene）,as a new type of two-dimensional material,has unique structure,metallic conductivity and abundant surface terminal groups,which is a kind of energy storage material with great potential.Therefore,the paper takes Ti₃C₂T_x in MXene family as the research object and does the following research work:（1）In order to solve the problem of easy restacking of Ti₃C₂T_x nanosheets,a CoS modified 3D MXene/carbon foam hybrid aerogel was prepared by in-situ growth and high temperature annealing in this part.The surface of the composite was characterized by a scanning electron microscope（SEM）,which confirmed that the introduction of CoS and carbon foam effectively prevented the restacking of Ti₃C₂T_x nanosheets.Then,the performance of the composite as the electrode material of supercapacitor was investigated by electrochemical test.The CoS-CMC-31:1 electrode material obtained a mass capacitance of 250 F g^-1 at the current density of 1 A g^-1,which is much higher than the pure MXene(91 F g^-1).Moreover,the electrode material displayed excellent cycling stability(retaining 97.50%of the initial capacitance after 10,000 cycles at a high current density of 10 A g^-1).In addition,an all-solid asymmetric supercapacitor composed of the electrode material and activated carbon retains 80.39%of its initial capacitance after 5,000cycles at a current density of 1 A g^-1.Moreover,the all-solid asymmetric supercapacitor shows an energy density of 10.66 Wh kg^-1 and a power density of 678.10 W kg^-1.In addition,two of the all-solid asymmetric supercapacitors in series can light a small light bulb,demonstrating the potential of the electrode material for practical applications in energy storage.（2）The pristine MXene films often suffer from poor ambient stability and mechanical properties that stem from their hydrophilic terminal groups and weak interlayer interactions.In order to solve this problem,a heteroatom doping strategy is developed to tailor the surface functionalities of MXene,followed by the addition of large-sized reduced graphene oxide（rGO）as conductive additives to achieve a scalable production of S,N-doped MXene/rGO hybrid films.The SNMG-40/rGO hybrid film exhibited a high mechanical strength（≈45 MPa）and an energy storage performance(698.5 F cm^-3).In addition,the hybrid film exhibits long-term cyclic stability(≈98%of initial capacitance after 30,000cycles at a scan rate of 100 m V s^-1)which can be maintained in ambient conditions or immersed in sulphuric acid electrolyte for more than 100 days.An asymmetric supercapacitor assembled by employing rGO and the hybrid film shows a high energy density of 22.3 Wh kg^-1 and a high power density of 7463.4 W kg^-1,which is much higher than MXene-based electrode materials previously reported.In addition,the asymmetric supercapacitor still has excellent mechanical durability under different deformation conditions.Thus,this strategy makes MXene materials more competitive in real-world applications.